WO2021131985A1

WO2021131985A1 - Method for producing polyarylene sulfide

Info

Publication number: WO2021131985A1
Application number: PCT/JP2020/047030
Authority: WO
Inventors: 佐藤　剛; 義紀鈴木
Original assignee: 株式会社クレハ
Priority date: 2019-12-26
Filing date: 2020-12-16
Publication date: 2021-07-01
Also published as: CN114787241A; CN114787241B; JPWO2021131985A1; KR20220107236A; US20230033026A1; JP7357695B2

Abstract

Provided is a method for producing polyarylene sulfide ("PAS" hereinafter), the method making it possible to shorten the time required for a cooling step for forming granular PAS and to suppress any increase in the average particle size of the resultant granular PAS.　The method for producing PAS according to the present invention includes: a first polymerization step for heating a mixture that contains an organic polar solvent, a sulfur source, water, a polyhaloaromatic compound, and an alkali metal hydroxide in the presence of at least one auxiliary agent selected from carboxylates, etc., to initiate a polymerization reaction so as to generate a reaction mixture that contains a prepolymer having a polyhaloaromatic compound conversion rate of 50 mol% or higher; a phase separation agent addition step for subsequently adding a phase separation agent to the reaction mixture; a second polymerization step for subsequently continuing the polymerization reaction; and a cooling step for subsequently cooling the reaction mixture. In the cooling step, the coolant is added to the reaction mixture at a temperature ranging from at least 5°C above the maximum thickening temperature to less than 250°C, and the cooling rate at the maximum thickening temperature ranges from 2.2°C/min to 6.0°C/min (inclusive).

Description

Method for producing polyarylene sulfide

The present invention relates to a method for producing polyarylene sulfide.

Polyphenylene sulfide (hereinafter, also referred to as "PAS") represented by polyphenylene sulfide (hereinafter, also referred to as "PPS") has heat resistance, chemical resistance, flame retardancy, mechanical strength, electrical properties, and dimensions. It is an engineering plastic with excellent stability. Since PAS can be molded into various molded products, films, sheets, fibers, etc. by general melt processing methods such as extrusion molding, injection molding, and compression molding, it can be used for electrical equipment, electronic equipment, automobile equipment, packaging materials, etc. It is widely used in a wide range of technical fields.

PAS is widely used as a metal substitute for reducing the weight of automobiles, especially in the field of automobiles. High molecular weight PAS with high toughness is required for in-vehicle applications. Patent Documents 1 and 2 disclose a method for producing granular PAS as a high molecular weight PAS.

Japanese Unexamined Patent Publication No. 2001-89569 Japanese Unexamined Patent Publication No. 2004-51732

In recent years, with the increase in demand for granular PAS, further shortening of the production of granular PAS is required. However, in the conventional manufacturing method, since it is necessary to perform slow cooling in the cooling step for forming the granular PAS by granulation for the purpose of controlling the particle size and improving the purity of the granular PAS, the cooling step is performed. It takes a long time.

On the other hand, it is known that when PAS is produced in the presence of a polymerization aid, a high molecular weight PAS can be obtained in a short time. However, the average particle size of the obtained PAS tends to increase, and as a result, the piping of the PAS manufacturing apparatus or the like tends to be clogged, and it takes a lot of time to clean the piping in order to remove the clogged PAS. is there.

The present invention has been made in view of the above problems, and it is possible to shorten the time required for the cooling step for forming granular PAS and to suppress an increase in the average particle size of the obtained granular PAS. It is an object of the present invention to provide a method for producing PAS which can be produced.

In the production of PAS, the present inventors perform a first polymerization step, a phase separator addition step, a second polymerization step, and cooling in the presence of at least one auxiliary agent selected from carboxylates and the like. The steps are performed in this order, and in the cooling step, a coolant is added to the reaction mixture at a temperature within a predetermined range, and the cooling rate at the maximum thickening temperature is 2.2 ° C./min or more and 6.0 ° C./min. It was found that the above object was achieved by the following, and the present invention was completed.

The method for producing PAS according to the present invention is
At least one selected from the group consisting of carboxylates, alkali metal chlorides, organic sulfonates, alkali metal sulfates, alkaline earth metal oxides, alkali metal phosphates, and alkaline earth metal phosphates. In the presence of the auxiliary agent, a mixture containing an organic polar solvent, a sulfur source, water, a polyhalo aromatic compound, and an alkali metal hydroxide is heated to initiate a polymerization reaction, and the conversion rate of the polyhalo aromatic compound is increased. The first polymerization step to produce a reaction mixture containing 50 mol% or more of prepolymer, and
After the first polymerization step, a phase separation agent addition step of adding a phase separation agent to the reaction mixture,
After the phase separation agent addition step, a second polymerization step in which the polymerization reaction is continued, and
A cooling step of cooling the reaction mixture after the second polymerization step is included.
In the cooling step, the coolant is added to the reaction mixture at a temperature higher than the maximum thickening temperature by 5 ° C. or more and lower than 250 ° C., and the cooling rate at the maximum thickening temperature is 2.2 ° C./min. It is 6.0 ° C./min or less.

In the method for producing PAS according to the present invention, a coolant may be added to the reaction mixture in the cooling step.

In the method for producing PAS according to the present invention, the coolant may be water and / or ice.

In the method for producing PAS according to the present invention, at the maximum thickening temperature, the content of the coolant in the reaction mixture may be 2.7 mol or more and 6.0 mol or less with respect to 1 mol of the sulfur source.

According to the present invention, there is provided a method for producing PAS, which can shorten the time required for the cooling step for forming granular PAS and can suppress an increase in the average particle size of the obtained granular PAS. be able to. As a result, the pipes of the PAS manufacturing apparatus and the like are less likely to be clogged, and the need to remove the clogged PAS is reduced, so that the time required for cleaning the pipes can be shortened. From the above, as a whole, the production of granular PAS can be shortened.

An embodiment of the method for producing PAS according to the present invention will be described below. The method for producing PAS in the present embodiment includes a first polymerization step, a phase separation agent addition step, a second polymerization step, and a cooling step as essential steps. The method for producing PAS in the present embodiment may include a dehydration step, a preparation step, a post-treatment step, and the like, if desired. Hereinafter, each material used in the present invention will be described in detail, and each step will be described in detail.

(Organic polar solvents, sulfur sources, polyhaloaromatic compounds, and alkali metal hydroxides)
As the organic protic solvent, the sulfur source, the polyhalo aromatic compound, and the alkali metal hydroxide, those usually used in the production of PAS can be used. Each of the organic polar solvent, the sulfur source, the polyhaloaromatic compound, and the alkali metal hydroxide may be used alone, or if it is a combination capable of producing PAS, two or more kinds may be mixed and used. You may.

Examples of the organic polar solvent include an organic amide solvent; an aprotic organic polar solvent composed of an organic sulfur compound; and an aprotic organic polar solvent composed of a cyclic organic phosphorus compound. Examples of the organic amide solvent include amide compounds such as N, N-dimethylformamide and N, N-dimethylacetamide; N-alkylcaprolactam compounds such as N-methyl-ε-caprolactam; and N-methyl-2-pyrrolidone (hereinafter, "" NMP ”), N-alkylpyrrolidone compounds such as N-cyclohexyl-2-pyrrolidone or N-cycloalkylpyrrolidone compounds; N, N-dialkylimidazolidinones such as 1,3-dialkyl-2-imidazolidinone. Compounds; tetraalkylurea compounds such as tetramethylurea; hexaalkylphosphate triamide compounds such as hexamethylphosphate triamide, and the like can be mentioned. Examples of the aprotic organic polar solvent composed of an organic sulfur compound include dimethyl sulfoxide and diphenyl sulfone. Examples of the aprotic organic polar solvent composed of the cyclic organic phosphorus compound include 1-methyl-1-oxophosphoran. Among them, an organic amide solvent is preferable in terms of availability, handleability, etc., and N-alkylpyrrolidone compound, N-cycloalkylpyrrolidone compound, N-alkylcaprolactam compound, and N, N-dialkylimidazolidinone compound are more preferable. , NMP, N-methyl-ε-caprolactam, and 1,3-dialkyl-2-imidazolidinone are even more preferred, with NMP being particularly preferred.

The amount of the organic polar solvent used is preferably 1 to 30 mol, more preferably 3 to 15 mol, with respect to 1 mol of the sulfur source, from the viewpoint of efficiency of the polymerization reaction and the like.

Examples of the sulfur source include alkali metal sulfide, alkali metal hydrosulfide, and hydrogen sulfide, and alkali metal sulfide and alkali metal hydrosulfide are preferable. The sulfur source can be handled in either an aqueous slurry state or an aqueous solution state, and is preferably in an aqueous solution state from the viewpoint of handleability such as measurable property and transportability. Examples of the alkali metal sulfide include lithium sulfide, sodium sulfide, potassium sulfide, rubidium sulfide, and cesium sulfide. Examples of the alkali metal hydrosulfide include lithium hydrosulfide, sodium hydrosulfide, potassium hydrosulfide, rubidium hydrosulfide, and cesium hydrosulfide.

A polyhalo aromatic compound refers to an aromatic compound in which two or more hydrogen atoms directly connected to an aromatic ring are substituted with halogen atoms, and an aromatic compound in which two hydrogen atoms directly connected to an aromatic ring are substituted with halogen atoms. Whether it is a compound (that is, a dihalo aromatic compound) or an aromatic compound in which three or more hydrogen atoms directly connected to an aromatic ring are substituted with halogen atoms (also referred to as "polyhalo aromatic compound having three or more halogen substitutions"). Good.

Examples of the polyhaloaromatic compound include o-dihalobenzene, m-dihalobenzene, p-dihalobenzene, dihalotoluene, dihalonaphthalene, methoxy-dihalobenzene, dihalobiphenyl, dihalobenzoic acid, dihalodiphenyl ether, dihalodiphenyl sulfone, and dihalo. Dihalo aromatic compounds such as diphenylsulfoxide and dihalodiphenylketone; 1,2,3-trichlorobenzene, 1,2,4-trichlorobenzene, 1,3,5-trichlorobenzene, hexachlorobenzene, 1,2,3 4-Tetrachlorobenzene, 1,2,4,5-tetrachlorobenzene, 1,3,5-trichloro-2,4,6-trimethylbenzene, 2,4,6-trichlorotoluene, 1,2,3-trichloronaphthalene , 1,2,4-trichloronaphthalene, 1,2,3,4-tetrachloronaphthalene, 2,2', 4,4'-tetrachlorobiphenyl, 2,2', 4,4'-tetrachlorobenzophenone, Examples thereof include polyhaloaromatic compounds having 3 or more halogen substitutions, such as 2,4,2'-trichlorobenzophenone. The halogen atom refers to each atom of fluorine, chlorine, bromine, and iodine, and two or more halogen atoms in the polyhalo aromatic compound may be the same or different. Among them, p-dichlorobenzene, m-dihalobenzene, and a mixture thereof are preferable, p-dichlorobenzene is more preferable, and p-dichlorobenzene (hereinafter, also referred to as "pDCB") is preferable in terms of availability, reactivity, and the like. Especially preferable.

The amount of the polyhalo aromatic compound used is preferably 0.90 to 1.50 mol, more preferably 0.92 to 1.10 mol, and even more preferably, with respect to 1 mol of the sulfur source charged. It is 0.95 to 1.05 mol. When the amount used is within the above range, the decomposition reaction is unlikely to occur, the stable polymerization reaction can be easily carried out, and the high molecular weight polymer can be easily produced.

Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, and cesium hydroxide.

(Dehydration process)
The dehydration step is a step of discharging at least a part of the distillate containing water from the inside of the system containing the mixture containing the organic polar solvent, the sulfur source, and the alkali metal hydroxide to the outside of the system before the preparation step. Is. The polymerization reaction between the sulfur source and the polyhalo aromatic compound is affected by the amount of water present in the polymerization reaction system, such as being promoted or inhibited. Therefore, it is preferable to reduce the amount of water in the polymerization reaction system by performing a dehydration treatment before the polymerization so that the amount of water does not inhibit the polymerization reaction.

In the dehydration step, it is preferable to perform dehydration by heating in an inert gas atmosphere. The water to be dehydrated in the dehydration step is water contained in each raw material prepared in the dehydration step, an aqueous medium of an aqueous mixture, water produced as a by-product by the reaction between each raw material, and the like.

The heating temperature in the dehydration step is not particularly limited as long as it is 300 ° C. or lower, and is preferably 100 to 250 ° C. The heating time is preferably 15 minutes to 24 hours, more preferably 30 minutes to 10 hours.

In the dehydration process, dehydration is performed until the amount of water is within a predetermined range. That is, in the dehydration step, the amount is preferably 0.5 to 2.4 mol with respect to 1.0 mol of the sulfur source (hereinafter, also referred to as "charged sulfur source" or "effective sulfur source") in the charged mixture (described later). It is desirable to dehydrate until it becomes. When the water content becomes too small in the dehydration step, water may be added in the preparation step prior to the polymerization step to adjust the water content to a desired level.

(Preparation process)
The charging step is a step of preparing a mixture containing an organic polar solvent, a sulfur source, and a polyhalo aromatic compound. The mixture charged in the charging process is also referred to as "prepared mixture".

When the dehydration step is performed, the amount of the sulfur source in the charged mixture (hereinafter, also referred to as "the amount of the charged sulfur source" or "the amount of the effective sulfur source") is determined from the molar amount of the sulfur source input as the raw material in the dehydration step. It can be calculated by subtracting the molar amount of hydrogen sulfide volatilized in.

When the dehydration step is performed, the alkali metal hydroxide and water can be added to the mixture remaining in the system after the dehydration step as needed in the preparation step. In particular, the alkali metal hydroxide can be added in consideration of the amount of hydrogen sulfide produced during dehydration and the amount of alkali metal hydroxide generated during dehydration. The number of moles of the alkali metal hydroxide is the number of moles of the alkali metal hydroxide added in the preparation step, and in the case of performing the dehydration step, the alkali metal hydroxide added as necessary in the dehydration step. It is calculated based on the number of moles of the alkali metal hydroxide generated by the production of hydrogen sulfide in the dehydration step. When the sulfur source contains alkali metal sulfide, the number of moles of alkali metal hydroxide per mol of sulfur source (charged sulfur source) shall be calculated including the number of moles of alkali metal sulfide. When hydrogen sulfide is used as the sulfur source, the number of moles of alkali metal hydroxide per mole of sulfur source (charged sulfur source) shall be calculated including the number of moles of alkali metal sulfide produced. .. However, the number of moles of the alkali metal hydroxide added for other purposes, for example, an embodiment of a combination of an organic carboxylic acid metal salt as a polymerization aid and / or an alkali metal hydroxide with an organic carboxylic acid and an alkali metal hydroxide. The number of moles of alkali metal hydroxide consumed in reactions such as neutralization shall not be included in the number of moles of alkali metal hydroxide per mole of sulfur source (prepared sulfur source). .. Further, when at least one acid selected from the group consisting of inorganic acids and organic acids is used for some reason, the alkali metal hydroxide required to neutralize the at least one acid is used. The number of moles shall not be included in the number of moles of alkali metal hydroxide per mole of the sulfur source (charged sulfur source).

In the charged mixture, the amounts of each of the organic polar solvent and the polyhalo aromatic compound used are set in the ranges shown in the above description regarding the organic polar solvent and the polyhalo aromatic compound, for example, with respect to 1 mol of the charged amount of the sulfur source. ..

(First polymerization step)
The first polymerization step consists of a group consisting of carboxylates, alkali metal chlorides, organic sulfonates, alkali metal sulfates, alkaline earth metal oxides, alkali metal phosphates, and alkaline earth metal phosphates. A mixture containing an organic polar solvent, a sulfur source, water, a polyhalo aromatic compound, and an alkali metal hydroxide is heated in the presence of at least one auxiliary agent of choice to initiate a polymerization reaction to initiate the polyhalo aromatic. This is a step of producing a reaction mixture containing a prepolymer having a conversion rate of a group compound of 50 mol% or more. In the first polymerization step, a polymerization reaction is carried out in a reaction system in which the produced polymer is uniformly dissolved in an organic polar solvent. In the present specification, the reaction mixture means a mixture containing a reaction product produced in the above-mentioned polymerization reaction, and the formation starts at the same time as the start of the above-mentioned polymerization reaction.

For the purpose of shortening the polymerization cycle time, a method using two or more reaction tanks may be used as the polymerization reaction method.

In the first polymerization step, the mixture prepared in the charging step, that is, the charged mixture is heated to a temperature of 170 to 270 ° C. to initiate the polymerization reaction, and the prepolymer having a conversion rate of the polyhalo aromatic compound of 50 mol% or more is started. It is preferable to generate. The polymerization temperature in the first polymerization step is preferably selected from the range of 180 to 265 ° C. in order to suppress side reactions and decomposition reactions.

The conversion rate of the polyhalo aromatic compound is preferably 50 to 98%, more preferably 60 to 97%, even more preferably 65 to 96%, and particularly preferably 70 to 95%. The conversion rate of the polyhalo aromatic compound is calculated based on the amount of the polyhalo aromatic compound remaining in the reaction mixture determined by gas chromatography, the residual amount, the amount of the polyhalo aromatic compound charged, and the amount of the sulfur source charged. Can be done.

During the polymerization reaction, the amount of at least one of water and the organic polar solvent may be changed. For example, water can be added to the reaction system during polymerization. However, in the first polymerization step, it is usually preferable to start the polymerization reaction using the charging mixture prepared in the charging step and end the reaction in the first polymerization step.

At the start of the first polymerization step, the water content is preferably 0.5 to 2.4 mol, more preferably 0.5 to 2.0 mol, per 1.0 mol of the sulfur source. , 1.0 to 1.5 mol, even more preferably. By setting the water content within the above range at the start of the first polymerization step, the sulfur source can be solubilized in an organic polar solvent and the reaction can proceed suitably.

The first stage polymerization step is a group consisting of carboxylates, alkali metal chlorides, organic sulfonates, alkali metal sulfates, alkaline earth metal oxides, alkali metal phosphates, and alkaline earth metal phosphates. It is carried out in the presence of at least one of the more selected auxiliaries. As a result, in the method for producing PAS according to the present invention, high molecular weight PAS can be easily obtained. From the viewpoint of availability, handleability, etc., the auxiliary agent is preferably a carboxylate.

As long as the auxiliary agent is present in the first-stage polymerization step, the step of adding the auxiliary agent is not particularly limited, and examples thereof include a dehydration step, a preparation step, and a first polymerization step.

The auxiliary agent may be added to the reaction system as the above-mentioned compound itself such as a carboxylate, or may be added to the reaction system in the form of a corresponding organic acid or inorganic acid to carry out alkali metal hydroxylation in the reaction system. It may be present in the first-stage polymerization step by producing a compound corresponding to an auxiliary agent by a neutralization reaction with a substance.

The amount of the auxiliary agent is preferably 0.1 to 50 mol%, more preferably 1 to 40 mol%, and even more preferably 5 to 30 mol% per 1 mol of the sulfur source. When the amount of the auxiliary agent is within the above range, the high molecular weight PAS is more likely to be obtained.

(Phase separator addition step)
The phase separation agent addition step is a step of adding the phase separation agent to the reaction mixture after the first polymerization step. The phase separating agent is not particularly limited, and is, for example, water, an organic carboxylic acid metal salt, an organic sulfonic acid metal salt, an alkali metal halide, an alkaline earth metal halide, an alkaline earth metal salt of an aromatic carboxylic acid, and a phosphoric acid. At least one selected from the group consisting of alkali metal salts, alcohols, and non-polar solvents can be mentioned. Of these, water is preferable because it is inexpensive and easy to post-treat. Further, a combination of an organic carboxylate and water, particularly a mixture containing an alkali metal carboxylate and water is also preferable. The above salts may be in the form of adding the corresponding acid and base separately.

Examples of the non-polar solvent include hydrocarbons, and in order to promote the reaction between prepolymers, it is easier to obtain a high-molecular-weight PAS when the non-polar solvent does not dissolve the prepolymer. Therefore, an aliphatic hydrocarbon Is preferable, alkanes (paraffinic hydrocarbons) are more preferable, and linear alkanes are even more preferable. The number of carbon atoms of hydrocarbons, aliphatic hydrocarbons, alkanes, and linear alkanes is particularly limited as long as hydrocarbons, aliphatic hydrocarbons, alkanes, and linear alkanes can be used as solvents in the second polymerization step. However, for example, 6 to 24 are mentioned, and from the viewpoint of handleability and the like, 7 to 20 is preferable, 8 to 18 is more preferable, 9 to 16 is even more preferable, and 10 to 14 is particularly preferable. Specific examples of the non-polar solvent include n-hexane, n-heptane, n-octane, isooctane, n-nonane, n-decane, n-dodecane, n-tetradecane, n-hexadecan, n-octadecan, and n-eicosane. , N-Tetradecane and the like, and since it is easy to obtain a higher molecular weight PAS and is excellent in handleability, availability, etc., isooctane, n-decane, and n-tetradecane are preferable, and n-decane and n-tetradecane are preferable. More preferred.

The amount of the phase separation agent used varies depending on the type of compound used, but is usually in the range of 1 to 10 mol with respect to 1 kg of the organic polar solvent. In particular, it is possible to adopt a method of adding water as a phase separation agent in the phase separation agent addition step so that the amount of water in the reaction system in the second polymerization step is more than 4 mol and 20 mol or less per 1 kg of the organic polar solvent. preferable. In the present invention, the phase separation agent contains water, and the molar ratio of water to the organic polar solvent in the phase separation agent addition step is 0.5 to 3.0, preferably 0.6 to 0.6 from the viewpoint of particle strength. It is 2.0, more preferably 0.65 to 1.5. By setting the amount of the phase separator used in the above range, PAS particles having high particle strength can be produced in a high yield.

When a mixture containing an alkali metal carboxylate and water is used as the phase separator, the amount of the mixture used is such that the amount of the alkali metal carboxylate is 30 mol or less per 1 mol of the sulfur source. It is preferable to adjust. The method for adding the phase separating agent according to the present embodiment is not particularly limited, and examples thereof include a method of adding the entire amount at a time and a method of adding the phase separating agent in a plurality of times.

(Second polymerization step)
The second polymerization step is a step of continuing the polymerization reaction after the step of adding the phase separator. In the second polymerization step, phase-separated polymerization is carried out in which the polymerization reaction is continued in a state where the inside of the reaction system is phase-separated into a polymer-rich phase and a polymer-lean phase in the presence of a phase-separating agent. Specifically, by adding a phase separator, the polymerization reaction system (polymerization reaction mixture) becomes a polymer-rich phase (phase mainly composed of molten PAS) and a polymer-lean phase (phase mainly composed of an organic polar solvent). Phase-separate.

Regarding the polymerization temperature in the second polymerization step, the polymerization reaction is continued by heating to 245 to 290 ° C., preferably 250 to 285 ° C., more preferably 255 to 280 ° C. The polymerization temperature may be maintained at a constant temperature, or may be raised or lowered stepwise as needed. From the viewpoint of controlling the polymerization reaction, it is preferable to maintain a constant temperature. The polymerization reaction time is generally in the range of 10 minutes to 72 hours, preferably 30 minutes to 48 hours.

From the viewpoint of improving the yield, the pH of the reaction mixture after the second polymerization step may be 8 to 11 or 9 to 10.5. The method for adjusting the pH of the reaction mixture is not particularly limited, and for example, a method for adjusting the content of alkali metal hydroxide in the charging step, or a method for adjusting the alkali metal hydroxide, an inorganic acid and / or an organic acid later. Can be mentioned as a method of adding.

(Cooling process)
The cooling step is a step of cooling the reaction mixture after the second polymerization step. In the cooling step, the liquid phase containing the produced polymer is cooled. In the cooling step, a coolant is added to the reaction mixture at a temperature higher than the maximum thickening temperature by 5 ° C. or higher and lower than 250 ° C., and the cooling rate at the maximum thickening temperature is 2.2 ° C./min or higher. It is 0 ° C./min or less.
By adding the coolant to the reaction mixture at a temperature within the above range and setting the cooling rate at the maximum thickening temperature within the above range, the time required for the cooling step for forming the granular PAS is shortened. And it is possible to suppress an increase in the average particle size of the obtained granular PAS.

The lower limit of the cooling rate is 2.2 ° C./min or more, preferably 2.3 ° C./min or more, more preferably 2.4 ° C./min or more, and even more preferably 2.5 ° C./min. Minutes or more, particularly preferably 2.6 ° C./min or more. When the cooling rate is 2.2 ° C./min or more, the time required for the cooling step for forming the granular PAS can be shortened, and the increase in the average particle size of the obtained granular PAS can be suppressed. Can be done. The upper limit of the cooling rate is not particularly limited, and may be, for example, 6.0 ° C./min or less, 5.0 ° C./min or less, 4.0 ° C./min or less, or 3.9 ° C./min or less.

In the cooling step, the profile of the cooling rate is not particularly limited as long as the coolant is added to the reaction mixture at a temperature within the above-mentioned predetermined range and the cooling rate at the maximum thickening temperature is within the above range. Therefore, the cooling rate at a temperature other than the maximum thickening temperature may be, for example, a cooling rate by natural air cooling, and may be the same as the cooling rate at the maximum thickening temperature from the viewpoint of shortening the time of the cooling step. Further, for example, in the case of cooling using a coolant described later, when the amount of the coolant added is limited due to the limited capacity of the reaction can, first natural air cooling is performed, and then the reaction can is cooled. When the temperature of the contents drops to the vicinity of the maximum thickening temperature, the cooling rate may be adjusted so that the cooling rate at a temperature exceeding the maximum thickening temperature is the same as the cooling rate at the maximum thickening temperature. At this time, the temperature for adjusting the cooling rate may be appropriately set according to the capacity of the reaction can, and for example, the maximum thickening temperature (maximum thickening temperature + 20 ° C.) or less can be mentioned. The maximum thickening temperature + 5 ° C.) or higher (maximum thickening temperature + 15 ° C.) may be used, the (maximum thickening temperature + 8 ° C.) or higher (maximum thickening temperature + 12 ° C.) or lower, or the maximum thickening temperature + 10 ° C. may be used.

In the cooling step, the coolant is added to the reaction mixture at a temperature that is 5 ° C. or higher and less than 250 ° C. above the maximum thickening temperature. Therefore, a cooling method such that the cooling rate at the maximum thickening temperature is 2.2 ° C./min or more and 6.0 ° C./min or less includes at least addition of a coolant to the reaction mixture. Cooling by adding a coolant may be carried out in combination with other cooling methods. Other cooling methods are not particularly limited, and for example, forced air cooling by an air flow generator such as a fan or a circulator; circulation of the refrigerant in the jacket of the polymerization reaction tank; reflux of the gas phase in the reaction mixture by the reflux condenser, etc. Can be mentioned. Above all, it is preferable to add a coolant to the reaction mixture because it is easy to prevent PAS from adhering to the wall surface due to cooling from the wall surface of the polymerization reaction tank. The coolant is not particularly limited, and water and / or ice; an organic polar solvent (for example, an organic amide solvent such as NMP) is preferable from the viewpoint of easy separation from PAS in the post-treatment step, and the specific heat and latent heat of evaporation are large. From the point of view, water and / or ice is more preferred. Further, water and / or ice are more preferable as the coolant from the viewpoint that the phase separation property of the reaction mixture is easily improved and the yield of PAS is easily improved.

At the maximum thickening temperature, the content of the coolant in the reaction mixture is preferably 2.7 mol or more and 6.0 mol or less with respect to 1 mol of the sulfur source, from the viewpoint that sufficient cooling is easily performed according to the amount. It is more preferably 3.0 mol or more and 5.5 mol or less, and even more preferably 4.0 mol or more and 5.0 mol or less.

In the present specification, the maximum thickening temperature refers to the stirring torque of the reaction mixture measured between 240 ° C. and 220 ° C. when the reaction mixture after the second polymerization step is cooled from 255 ° C. by natural air cooling. The temperature at which the stirring torque is maximized.

(Post-treatment process (separation process, cleaning process, recovery process, etc.))
In the method for producing PAS in the present embodiment, the post-treatment step after the polymerization reaction can be carried out by a conventional method, for example, by the method described in JP-A-2016-0562332.

(Obtained PAS)
The PAS obtained by the method for producing PAS in the present embodiment has an average particle size of preferably 2000 μm or less, more preferably 1800 μm or less, and even more preferably 1500 μm or less. The lower limit of the average particle size of the PAS is not particularly limited, and may be, for example, 200 μm or more, 300 μm or more, or 400 μm or more. In this specification, the average particle size means a value measured by sieving as described in Examples described later.

The PAS obtained by the method for producing PAS in the present embodiment has ^{a melt viscosity measured at a temperature of 310 ° C. and a shear rate of 1,216 sec -1} , preferably 1000 Pa · s or less, more preferably 300 Pa · s or less, and even more preferably. Is 150 Pa · s or less. The lower limit of the melt viscosity of the PAS is not particularly limited, and may be, for example, 1 Pa · s or more, 5 Pa · s or more, or 8 Pa · s or more. In the present specification, the melt viscosity means a value measured at the above temperature and a shear rate using a capillograph using about 20 g of a dry polymer of PAS.

The PAS obtained by the method for producing PAS in the present embodiment can be used as it is, or after being oxidatively crosslinked, it can be used alone or, if desired, by blending various inorganic fillers, fibrous fillers and various synthetic resins, and various injection moldings. It can be molded into products or extruded products such as sheets, films, fibers, and pipes.

In the method for producing PAS in the present embodiment, PAS is not particularly limited and is preferably PPS.

The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the claims, and the embodiment obtained by appropriately combining the disclosed technical means is also the present invention. Included in the technical scope. In addition, all the documents described in the present specification are incorporated by reference.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. The present invention is not limited to the examples. Unless otherwise specified, the operations in Examples and Comparative Examples were carried out at room temperature. Further, in the present specification, the weight average molecular weight (hereinafter, also referred to as “Mw”) means a polystyrene-equivalent weight average molecular weight measured by gel permeation chromatography.

(1) Melt Viscosity The melt viscosity of PAS was measured by Capilliograph (registered trademark) 1D manufactured by Toyo Seiki Seisakusho Co., Ltd., which was equipped with a nozzle having a diameter of 1.0 mm and a length of 10.0 mm as a capillary. The set temperature was 310 ° C. The polymer sample was introduced into the apparatus, held for 5 minutes, and then the melt viscosity was measured at a ^{shear rate of 1,200 sec -1.}

(2) Average particle size The average particle size of PAS is 2,800 μm (7 meshes (mesh / inch)) and 1,410 μm (12 mesh (mesh / inch)) as the sieve used. , Sift opening 1,000 μm (16 mesh (mesh / inch)), Simming opening 710 μm (24 mesh (mesh / inch)), Simming opening 500 μm (32 mesh (mesh / inch)), Sift Opening 250 μm (60 mesh (mesh / inch)), sieving opening 150 μm (100 mesh (mesh / inch)), sieving opening 105 μm (145 mesh (mesh / inch)), sieving opening 75 μm (200 mesh) (Number of meshes / inch)), measured by the sieving method using a sieve with a mesh size of 38 μm (400 mesh (number of meshes / inch)), and the cumulative mass is 50% mass from the mass of the sieving material of each sieving. The average particle size at the time of

[Example 1]
(Dehydration process)
In a 20 liter autoclave, add 6,005 g of NMP, 2,003 g of sodium hydrosulfide aqueous solution (NaSH: purity 62.24% by mass), 1,071 g of sodium hydroxide (NaOH: purity 73.40% by mass), and 180 g of sodium acetate. I prepared it. After replacing the inside of the autoclave with nitrogen gas, over a period of about 4 hours while stirring at a rotation speed of 250rpm by a stirrer, the temperature was gradually raised to 200 ° C., water _{(H 2 O) 902g, NMP763g} , and hydrogen sulfide ( H ₂ S) to distill 15 g.

(First polymerization step)
After the dehydration step, the contents of the autoclave are cooled to 150 ° C., pDCB 3,244 g, NMP 3,302 g, sodium hydroxide 8 g, and water 107 g are added, and the temperature is raised to 220 ° C. with stirring, and then to 260 ° C. 1 The temperature was raised in 5 hours, and the first polymerization step was performed. The ratio (g / mol) of NMP / charged sulfur source (hereinafter abbreviated as “prepared S”) in the can is 391, pDCB / charged S (mol / mol) is 1.010, and H ₂ O / charged. S (molar / mol) was 1.50. The conversion rate of pDCB in the first polymerization step was 93%.

(Phase separator addition step)
After the completion of the first polymerization step, 60 g of sodium hydroxide and 445 g of ion-exchanged water were press-fitted while stirring the contents of the autoclave, and the rotation speed of the stirrer was increased to 400 rpm. H ₂ O / NMP (mol / mol) was 0.67, and H ₂ O / charged S (mol / mol) was 2.63.

(Second polymerization step)
After press-fitting the ion-exchanged water, the contents of the autoclave were heated to 265 ° C. and reacted for 2.5 hours to carry out the second polymerization step.

(Cooling process)
After the completion of the second polymerization step, the contents of the autoclave are cooled from 265 ° C. at a cooling rate of 0.56 ° C./min by natural air cooling, and when the temperature of the contents reaches the maximum thickening temperature + 10 ° C., H _{Water at room temperature was press-fitted into the autoclave so that 2} O / charged S (mol / mol) was 2.63 to 5.00 to increase the cooling rate, and then cooling was performed to room temperature. The cooling rate at the maximum thickening temperature was 2.6 ° C./min.

The method for measuring the maximum thickening temperature is as follows. In the reaction can after the completion of the polymerization reaction, which is accompanied by a phase-separated polymerization system capable of producing a high-molecular-weight PAS, the PAS exists in a molten state and is phase-separated into a concentrated phase and a dilute phase by a phase separating agent. ,It has been known. Then, when the system is cooled under stirring, PAS solidifies from the molten state and exists in a suspended state as a powdery, particulate or granular solid, but in this process, the viscosity of the system changes. Occur. That is, when the dispersion system containing the molten PAS is cooled under stirring, the apparent viscosity of the entire system gradually increases due to the thickening of the PAS accompanying the cooling, and when a certain temperature is reached, the apparent viscosity of the entire system decreases. become. The maximum thickening temperature of this system can be detected as a stirring torque under constant stirring or as a power supply to the stirrer. The maximum thickening temperature was measured in advance based on the maximum value of power consumption measured by installing a clamp wattmeter CW140 (Yokogawa Electric Co., Ltd.) in an autoclave stirrer motor.

(Post-treatment process)
After the cooling step, the contents of the autoclave were sieved with a screen having an opening diameter of 150 μm (100 mesh), washed with acetone and ion-exchanged water, washed with an acetic acid aqueous solution, and dried for 24 hours to obtain granular PPS. Table 1 shows the conditions and the like in the cooling step, and Table 2 shows the physical characteristics and the like of the granular polymer (the same applies hereinafter).

[Example 2]
In the cooling step, granular PPS was obtained in the same manner as in Example 1 except that ice water was press-fitted into the autoclave instead of room temperature water, and forced air cooling of the autoclave was started at the same time as the press-fitting of ice water. It was. The cooling rate at the maximum thickening temperature was 3.9 ° C./min.

[Example 3]
Granular PPS was obtained in the same manner as in Example 1 except that the temperature at which water at room temperature was press-fitted was changed to the maximum thickening temperature + 20 ° C. The cooling rate at the maximum thickening temperature was 2.8 ° C./min.

[Example 4]
Granular PPS was obtained in the same manner as in Example 1 except that the temperature at which water at room temperature was press-fitted was changed to the maximum thickening temperature + 5 ° C. The cooling rate at the maximum thickening temperature was 2.7 ° C./min.

[Comparative Example 1]
In the cooling step, granular PPS was obtained in the same manner as in Example 1 except that the contents of the autoclave were cooled from 265 ° C. to room temperature at a cooling rate of 0.56 ° C./min by natural air cooling. The cooling rate at the maximum thickening temperature was 0.56 ° C./min.

[Comparative Example 2]
In order to confirm the effect of the increase in water content in the cooling step, in the cooling step, immediately after the completion of the second polymerization step, room temperature water was press-fitted into the autoclave to H ₂ O / charge S (mol). / Mol) was set to 2.63 to 5.00, and the same as in Example 1 except that the cooling rate at the maximum thickening temperature was 0.54 ° C./min, which was close to the value in Comparative Example 1. Granular PPS was obtained.

[Comparative Example 3]
In order to confirm the effect of the cooling rate, in the cooling process, _{instead of press-fitting room temperature water into the autoclave so that H 2} O / charged S (mol / mol) becomes 2.63 to 5.00, a fan is used. Granular PPS was obtained in the same manner as in Example 1 except that the autoclave was forcibly air-cooled and the cooling rate at the maximum thickening temperature was 1.7 ° C./min.

[Comparative Example 4]
As a result of adjusting the press-fitting speed of water in the cooling step in order to confirm the cooling rate required to suppress the increase in the average particle size of the granular PAS, the cooling rate at the maximum thickening temperature was 1.8 ° C./min. Granular PPS was obtained in the same manner as in Example 1 except that it was present.

[Comparative Example 5]
In order to confirm the addition temperature of the coolant required to suppress the increase in the average particle size of the granular PAS, the water addition temperature is added to 250 ° C. in the cooling step, and after the water is added, the autoclave is forcibly air-cooled by a fan. Granular PPS was obtained in the same manner as in Example 1 except for the above.

As is clear from Tables 1 and 2, according to the method for producing PAS according to the present invention, the time required for the cooling step for forming granular PAS can be shortened, and the average particle size of the obtained granular PAS can be shortened. Can be suppressed from increasing.

Claims

At least one selected from the group consisting of carboxylates, alkali metal chlorides, organic sulfonates, alkali metal sulfates, alkaline earth metal oxides, alkali metal phosphates, and alkaline earth metal phosphates. In the presence of the auxiliary agent, a mixture containing an organic polar solvent, a sulfur source, water, a polyhalo aromatic compound, and an alkali metal hydroxide is heated to initiate a polymerization reaction, and the conversion rate of the polyhalo aromatic compound is increased. The first polymerization step to produce a reaction mixture containing 50 mol% or more of prepolymer, and
After the first polymerization step, a phase separation agent addition step of adding a phase separation agent to the reaction mixture,
After the phase separation agent addition step, a second polymerization step in which the polymerization reaction is continued, and
A cooling step of cooling the reaction mixture after the second polymerization step is included.
In the cooling step, the coolant is added to the reaction mixture at a temperature higher than the maximum thickening temperature by 5 ° C. or more and lower than 250 ° C., and the cooling rate at the maximum thickening temperature is 2.2 ° C./min. A method for producing a polyarylene sulfide having a temperature of 6.0 ° C./min or less.
The method for producing polyarylene sulfide according to claim 1, wherein a coolant is added to the reaction mixture in the cooling step.
The method for producing polyarylene sulfide according to claim 2, wherein the coolant is water and / or ice.
The production of polyarylene sulfide according to claim 2 or 3, wherein at the maximum thickening temperature, the content of the coolant in the reaction mixture is 2.7 mol or more and 6.0 mol or less with respect to 1 mol of the sulfur source. Method.